Braking band, a ventilated disk-brake disk, and a core box for the production of a disk-brake disk core

ABSTRACT

A braking band with a remarkable capacity for improved cooling, for use in disk-brake disks, comprises two plates coaxial with an axis, facing one another, and spaced apart to form a space in which an air-flow takes place from the axis towards the outer side of the band, the plates having facing surfaces from which pillar-like elements extend, transversely, to connect the plates, the pillar-like elements being distributed in circular rings or rows concentric with the plates so as to be distributed uniformly in the space, those pillar-like elements which are disposed in inside rows of the braking band having rhombic cross-sections. Radial ends of the cross-sections of adjacent rows are substantially aligned on a common circle, and the pillar-like elements of each row have substantially the same radial extent in the said cross-section.

[0001] The present invention relates to a braking band and to aventilated disk-brake disk, particularly but not exclusively forapplications in the automotive field. A further aspect of the presentinvention relates to a core box for the production of a disk-brake diskcore.

[0002] As is known, a disk of the type specified above is constituted bytwo coaxial portions. A first portion, the support bell, is forconnection to the wheel hub of a vehicle, and the remaining, peripheralportion, the so-called braking band, is for cooperating with thedisk-brake calipers in order to exert the braking force on the vehicle.More particularly, the present invention relates to a so-calledventilated disk, that is, a disk in which the braking band isconstituted by two facing, coaxial plates, spaced apart so as to form aspace. The two plates are connected by pillar-like elements which extendthrough the space between the two plates. Ventilation ducts are thuscreated between the plates and air flows through the ducts in adirection from the inner side of the braking band towards the outerside, thus helping to dissipate to the environment the heat generated inthe band upon each braking operation.

[0003] Pillar-like elements of various shapes, of various sizes, anddistributed variously around the space in the braking band are known.Disk-brake disks in which the pillar-like elements are in a quincuncialarrangement and in three rows are known. Moreover, the shape of thecross-section of each pillar-like element, taken in an areasubstantially parallel to the direction of the air-flow through thespace, varies from row to row. In particular, the elements of the innerrow have a cross-section which is tapered towards the outer side of thebraking band.

[0004] A disk of this type is described, for example, in U.S. Pat. No.4,865,167. Disks with pillar-like elements of different radial extent,which are rounded towards the interior of the braking band are alsoknown. A disk of this type is described, for example, in U.S. Pat. No.6,152,270. Other disks provided with pillar-like elements are known fromEP-A-0318687, EP-A-0989321, and DE-A-4210449. Although these known disksare satisfactory from some points of view, they have considerabledisadvantages.

[0005] First of all, poor resistance of the braking band to thermalstresses and, in some extreme cases, to mechanical stresses has beennoted, this poor resistance being caused mainly by the known geometricalarrangement of the elements connecting the plates. Moreover, poorventilation efficiency or, in other words, a poor cooling capacity hasbeen noted, due to the resistance offered to the flow of air inside thespace present in the braking band, which resistance is caused by theknown shape of the elements connecting the plates.

[0006] As is also known, disk-brake disks are produced by casting andthe ventilation ducts between the two plates are formed during casting,with the use of a core. The core in turn is formed by the injection ofcore sand, that is, an agglomerate of sand and resins, into a core box.The latter is constituted by two half-shells which, when coupled, defineinside them a cavity which reproduces, amongst other things, theinternal structure of the disk and, in particular, the space between thetwo plates. The two half-shells consequently have projecting elementsfor defining cavities in the core which, when the disk is cast will formthe pillar-shaped elements connecting the two plates. During theproduction of the core, the core sand is injected into the two coupledhalf-shells by being made to flow from the innermost diameter to theoutermost diameter. When the sand starts to flow through the cavitywhich will define the space between the two plates, the projectingelements and, in particular, the inner row, consequently cause anobstruction to the flow of sand. The core-moulding step is thereforecritical, because of the above-mentioned obstructions. In fact, the sandwhich is in the vicinity of the pillar-like elements of the outermostrow and, in particular, in the region facing outwardly relative to thedisk, does not have the necessary compactness to withstand the castingof the molten metal. During casting, the flow of molten metal may infact undermine the less compact regions of the core and replace them,giving rise to undesired protuberances which adversely affect thefurther processing steps and the operation of the disk. Theprotuberances may cause obstructions in the first subsequent processingstep in which the disk is gripped and located by restraining elementswhich are inserted in the space between the plates. Moreover, theprotuberances may, for example, lead to an imbalance in the masses ofthe disk so that a larger amount of material has to be removed in thebalancing step at the end of the processing cycle. Finally, when thedisk is in use, the presence of these protuberances may constitute anobstruction to the air-flow through the ventilation ducts, giving riseto disturbances in the flow with a consequent reduction in coolingefficiency.

[0007] It is clear form the foregoing that, to prevent theabove-mentioned disadvantages, there is a particular requirement in thisfield to achieve a correct degree of compactness in every portion of thecore which will subsequently be used during the casting of a disk-brakedisk.

[0008] The object of the present invention is to devise and to provide abraking band, a ventilated disk-brake disk, and a core box for theproduction of a disk-brake disk core which satisfy the above-mentionedrequirements and, at the same time, prevent the problems mentioned withreference to the prior art.

[0009] This object is achieved by means of a braking band for adisk-brake disk according to claim 1, by means of a ventilateddisk-brake disk according to claim 19, and by means of a core box forthe production of a disk-brake disk core according to claim 22.

[0010] Further characteristics and the advantages of the band, of thedisk, and of the core box according to the invention will become clearfrom the following description of a preferred embodiment thereof, givenby way of non-limiting example with reference to the appended drawings,in which:

[0011]FIG. 1 is a partially-sectioned, perspective view of a disk-brakedisk according to the present invention,

[0012]FIG. 2a is a partially-sectioned, front view of the disk of FIG.1,

[0013]FIG. 2b is a partially-sectioned front view of a disk according toa further embodiment,

[0014]FIG. 3 is a section through the disk, taken on the line III-III ofFIG. 2,

[0015]FIG. 4 is a section through a possible variant of the disk of FIG.3,

[0016]FIG. 5 is a diametral section through a core box according to thepresent invention,

[0017]FIG. 6 shows the core box of FIG. 5 in a different operativecondition,

[0018]FIG. 7 is a diametral section through a core produced by the corebox of FIGS. 5 and 6,

[0019]FIG. 8 shows, in diametral section, a disk-brake disk at the stageof its production by casting,

[0020]FIG. 9 is a partially-sectioned, perspective view of a detail ofthe core box,

[0021]FIG. 10 is a partially-sectioned, side view of the detail of FIG.9, and

[0022]FIG. 11 is a partially-sectioned, perspective view of a seconddetail of the core box, and

[0023]FIGS. 12 and 13 show the behaviour of the vectors of the velocityof the air which passes through a ventilation duct in a solutionaccording to the prior art and according to the present invention,respectively.

[0024] With reference to the above-mentioned drawings, a disk-brake diskaccording to the present invention, in particular, a so-calledventilated disk for use in a disk brake (not shown) of a vehicle such asa motor car, is generally indicated 10. The disk 10 is substantiallycircular and extends about an axis indicated Z-Z in the drawings. Thedisk 10 comprises a support bell 12 and a braking band 14 coaxial withthe bell 12. The braking band 14, which is intended to cooperate withthe disk-brake calipers in order to exert the braking force on thevehicle, comprises a first plate 16 and a second plate 18 arrangedcoaxially on the axis Z-Z. The first plate 16 is on the same side as thebell support 12 and the second plate 18 is on the opposite side. The twoplates face one another and are spaced apart to form a space 20 in whichan air-flow takes place from the axis Z-Z towards the outer side of thebraking band 14 during the rotation of the disk. The two plates havefacing surfaces 22 from which pillar-like elements 24, 26 and 28, alsocommonly known as pins, extend transversely. The pillar-like elementsextend to connect the two plates. In particular, the first plate isformed continuously with the support bell 12 and the second plate 18 isconnected to the first by means of the pillar-like elements.

[0025] The pillar-like elements are distributed uniformly around thefacing surfaces 22 of the plates and, in the embodiment shown, aredivided into three concentric, circular rings or rows corresponding toan inner row, that is, the row closest to the axis Z-Z, an intermediaterow, and an outer row, that is, the row farthest from the axis Z-Z. Forsimplicity of description, the pillar-like elements of the inner row areindicated 24, the pillar-like elements of the intermediate row areindicated 26 and, finally, the pillar-like elements of the outer row areindicated 28.

[0026] According to one embodiment, the pillar-like elements comprisemore than one intermediate row (intermediate pillar-like elements 26),for example two intermediate rows disposed between the inner row (theinner pillar-like elements 24) and the outer row (the outer pillar-likeelements 28).

[0027] The pillar-like elements 24 of the inner row constitutepillar-like elements which are disposed in the vicinity of the edge ofthe braking band 14 that faces the axis Z-Z. The cross-section of eachof these pillar-like elements in an area substantially parallel to thedirection of the air-flow in the space is tapered towards the axis Z-Z.In greater detail, the pillar-like elements have a cross-section whichis tapered both towards the axis Z-Z of the plates and towards the outerside of the braking band 14, forming a substantially rhombiccross-section.

[0028] According to one embodiment, the pillar-like elements 24, 26arranged in inside rows of the band, meaning the inner row and the atleast one intermediate row, have rhombic cross-sections, cross-sectionmeaning a section considered in an area substantially parallel to thedirection of the air-flow through the space 20, as will be describedfurther below.

[0029] The rhombic cross-section is a cross-section which has four atleast partially flat sides. A pillar-like element having a rhombiccross-section is an element which has a lateral surface or wallcomprising four at least partially flat faces suitable for defining aventilation duct of the braking band and suitable for directing theair-flow from the interior towards the exterior of the disk in themanner which will be described in greater detail below.

[0030] According to one embodiment, the pillar-like elements 24, 26 havelinked flat surfaces defining the rhombic cross-section.

[0031] In particular, according to one embodiment, the pillar-likeelements 24, 26 of the inner and intermediate rows have, in a radialdirection, ends with link radii R1 variable from 1.5 mm to 2.5 mm andpreferably 2 mm. The pillar-like elements 28 of the outer row have, in aradial direction, a first end with a link radius R1 variable from 1.5 mmto 2.5 mm and preferably 2 mm, and a second end, preferably the outerend, with a link radius R4 variable from 4 mm to 5 mm and preferably 4.5mm. The pillar-like elements 24 of the inner row have, in a directiontransverse the direction of flow, link radii R2 variable from 3 mm to3.5 mm between the flat surfaces. The pillar-like elements 26 of the atleast one intermediate row have, in a direction transverse the directionof flow, link radii R3 variable from 3.5 to 4 mm between the flatsurfaces.

[0032] Preferably, all of the pillar-like elements 24, 26, 28 areconnected to the plates 16, 18 with link radii R5 variable from 3 mm to4 mm, preferably 3.5 mm (FIGS. 3 and 4).

[0033] Advantageously, the radial ends of the cross-sections of adjacentrows, considered in an area substantially parallel to the direction ofthe air-flow through the space 20-, are substantially aligned on thesame circle C2 or C3 (FIG. 2b). In other words, between adjacent rows,for example, the inner row and the intermediate row, or the intermediaterow and the outer row, there is no overlap in a tangential directionbetween the pillar-like elements 24 and 26 or 26 and 28 (any circleconcentric with the axis Z-Z of the plates 16, 18 and extending throughpillar-like elements of one row does not extend through pillar-likeelements of another row).

[0034] With further advantage, each of the pillar-like elements 24, 26,28 of each row has substantially the same radial extent D in the saidcross-section. In other words, the connecting elements of the plates areconnecting areas for the plates, and hence also stiffening areas, whichare distributed uniformly over the extent of the plates as a whole.

[0035] Moreover, according to one embodiment, the rhombic cross-sectionsof the pillar-like elements 24, 26 which are in inside rows of the band14 are symmetrical with respect to an axis transverse the direction offlow and each element 24, 26, 28 suitable for connection between theplates 16, 18 extends from one plate to the other 16, 18, whilstremaining inside the space 20. In other words, starting from a centralportion of maximum tangential extent or largest dimension, a pillar-likeelement of the inside rows of the band (the inner row, or row closest tothe axis Z-Z and the at least one intermediate row) is tapered towardsthe interior and towards the exterior of the disk with portions of equalextent and advantageously together forming pairs of parallel facesarranged for directing air in a controlled manner through the ducts orchannels defined in the space. Moreover, each element which serves forthe connection of the plates does not project or protrude outside thespace 20, avoiding the formation of elements for diverting the air-flowwhich project from the space to the exterior of the plates. In otherwords, the inner opening and the outer opening of the space 20 are freeof obstacles to the free circulation of the air-flow.

[0036] Advantageously, the pillar-like elements 24, 26, 28 interconnectthe plates 16, 18 over an area no greater than 15%-25%, preferably 20%of the total facing surface area of each plate. In other words, thefacing plates, which have an overall inner lateral surface area(substantially equal to an outer surface area suitable for interactingwith pads of a braking system or braking surface), are covered by theconnecting elements over an area variable from 15% to 25% and preferably20% of the overall area of the facing surface.

[0037] According to one embodiment, the two plates 16, 18 are connectedby pillar-like elements 24, 28 disposed along at least one inner row andone outer row which are concentric with one another.

[0038] According to a further embodiment, one or two furtherintermediate rows of pillar-like elements 26 are provided.

[0039] Preferably, the pillar-like elements 26 of the at least oneintermediate row are offset relative to those 24, 28 of the inner andouter rows.

[0040] With further advantage, the pillar-like elements 24, 26, 28 aredistributed between the two plates 16, 18 in a quincuncial arrangement.

[0041] According to one embodiment, an angle A2 of between 9 degrees and13 degrees, and preferably of 11 degrees, 36 minutes and 46 seconds, isprovided between two adjacent elements of the same row.

[0042] According to a further embodiment, an angle A1 of between 3degrees and 7 degrees and preferable equal to 5 degrees 48 minutes and23 seconds is provided between adjacent pillar-like elements ofdifferent rows.

[0043] The dimensions of the pillar-like elements may vary on the basisof the vehicle for which the disk is intended. For example, thedimension in the circumferential direction, that is, the shorterdiagonal d of the rhombus, has a value which is variable in dependenceon the type of vehicle, for example, 6 mm for a motor car or 10-12 mmfor a commercial vehicle, whereas the dimension in a radial direction,that is, the longer diagonal D, has a value which depends on the width hof the braking band, meaning the difference between the outside radiusand the inside radius of the braking band. The sides of the rhombiccross-section are linked together.

[0044] According to one embodiment, the pillar-like elements 24 of theinner row have, in an area substantially parallel to the direction ofthe air-flow through the space 20., a diagonal “d” of the rhombiccross-section transverse the direction of flow having dimensions ofbetween 6 mm and 7 mm. According to a further embodiment, thepillar-like elements 26 of the at least one intermediate row have, in anarea substantially parallel to the direction of the air-flow through thespace 20, a diagonal “d2” of the rhombic cross-section transverse thedirection of flow having dimensions of between 7 mm and 8 mm. Accordingto yet a further embodiment, the pillar-like elements 28 of the outerrow have, in an area substantially parallel to the direction of theair-flow through the space 20, a dimension “d3” of the cross-section,considered transverse the direction of the air-flow, of between 9 mm and10 mm.

[0045] This cross-section is shown, by way of example, in FIGS. 2a and 2b, which are front views of the disk and of the braking band in whichthe second plate 18 has been partially sectioned to show the shapes ofthe pillar-like elements of the at least three rows. This cross-sectiontherefore corresponds to the above-mentioned area substantially parallelto the direction of the air-flow through the space and may correspond toa plane transverse the axis Z-Z of the disk, or to an arcuate area, independence on the shapes adopted by the two plates and by the space.

[0046] The cross-section of each of the pillar-like elements 28 of theouter row in an area substantially parallel to the direction of theair-flow through the space is drop-shaped. In particular, thiscross-section is tapered towards the axis Z-Z of the plates and has anouter link portion, for example, with a radius of 5 mm (FIG. 2a).

[0047] Moreover, the cross-section of each of the pillar-like elements26 of the intermediate row in an area substantially parallel to thedirection of the air-flow through the space is tapered both towards theaxis Z-Z of the plates and towards the outer side of the braking band.The pillar-shaped elements of the intermediate row thus also have asubstantially rhombic cross-section similar to that of the pillar-likeelements of the inner row.

[0048] The following are some possible definitions of the areasubstantially parallel to the direction of the air-flow through thespace.

[0049] The embodiment of FIG. 3 in fact has a disk in which the twoplates constituting the braking band are substantially parallel toplanes perpendicular to the axis Z-Z and the space 20 correspondinglyextends in a ring coaxial with the axis Z-Z. The connection between thefirst plate 16 and the bell 12 is formed between walls which aresubstantially perpendicular to one another, although they are suitablylinked. In this configuration, the facing surfaces 22 of the two platesextend in two planes from which the pillar-like elements 24-28 projectperpendicularly. According to this embodiment, the air-flow enters thespace 20 in the vicinity of the region closest to the axis Z-Z andpasses through it towards the outer side of the braking band. As aresult, an area substantially parallel to the direction of the air-flowthrough the space 20 could be constituted by the median plane of thespace, indicated by a line 30 in FIG. 3.

[0050] The example of FIG. 4 shows a further embodiment of the disk inwhich, with respect to the axis Z-Z, an outer portion of the first plate16 is substantially parallel to planes perpendicular to the axis. Z-Z,whereas an inner portion of the first plate 16 deviates, curving towardsthe second plate 18. The space 20 correspondingly extends in a ringcoaxial with the axis Z-Z at least in the outer portion of the bandwhereas, in the region of the deviation of the first plate 16, the spacedeviates away from the bell. In fact, the connection between the firstplate 16 and the bell is formed between walls which are substantiallyinclined to one another and suitably linked. In this configuration, thesurface 22 of the second plate 18 extends in a plane perpendicular tothe axis Z-Z, whereas the surface 22 of the first plate has a curvedshape. The three rows of pillar-like elements are distributed over theentire extent of the braking band. In particular, the innermost row,indicated by the pillar-like elements 24, also follows the shape of thearcuate portion of the space, by virtue of its shape, tapered towardsthe inner side of the braking band. In an embodiment of this type, theair-flow enters the space in the vicinity of the region closest to theaxis Z-Z, which is arranged almost facing the front of the disk, andpasses through the space towards the outer side of the band. As aresult, an area substantially parallel to the direction of the air-flowthrough the space could be constituted, for example, by the central areaof the space, which is indicated by a line 32 in FIG. 4.

[0051] In the embodiment shown, with reference, for example, to FIG. 2,the pillar-shaped elements of the intermediate row are offset relativeto those of the inner row and of the outer row. In particular, thepillar-like elements 24, 26 and 28 are distributed between the twoplates in a quincuncial arrangement.

[0052] Moreover, as shown in FIGS. 1 to 4, the bell 12 and the brakingband 14 are formed as a single element, produced by casting, in whichthe braking band extends continuously from the support bell.

[0053] The connecting portion between the bell and the braking band mayadopt different configurations two of which are shown, for example, inFIGS. 3 and 4, as described above.

[0054] As will be appreciated from the foregoing description, by virtueof the provision of a braking band provided with plates connected bypillar-like connection elements which are disposed in adjacent rows inwhich the radial ends of the cross-sections are substantially aligned onthe same circle, and in which each of the pillar-like elements 24, 26,28 of each row has substantially the same radial extent in the saidcross-section, it is possible to overcome the disadvantages of the disksof the prior art and, in particular, a remarkable improvement has beenfound in the resistance of the braking band, for example, to the largestresses caused by considerable thermal gradients, as well as a lowincidence of splitting or cracking in the plates even when they arestressed by severe and repeated braking operations.

[0055] Moreover, by virtue of the provision of a braking band havingplates connected by pillar-like connecting elements which are disposedentirely within the space and, in the case of the pillar-like elementsof the inside rows, are of symmetrical rhombic shape, it is possible toovercome the disadvantages of the disks of the prior art and, inparticular, a remarkable improvement has been found in the air-flowthrough the ventilation ducts or channels of the space.

[0056] As can be seen from FIGS. 12 and 13, which compare tests on thebehaviour of the air-flow in a ventilation duct or channel provided inthe space between two plates of a disk having a geometrical arrangementaccording to the prior art (FIG. 12, in which similar elements areindicated by the same reference numerals with an apostrophe) and a diskhaving a geometrical arrangement according to the present invention(FIG. 13), the remarkable improvement in the ventilation achieved by thegeometrical arrangement of the solution proposed herein is clearlyshown. In particular, FIGS. 12 and 13 show the vector field of thevelocity of the air-flow which passes through a portion of space of aknown disk and of the disk having the geometrical arrangement resultingfrom the solution proposed herein, which field is repeatedcircumferentially throughout the space. The comparative test between theknown geometrical arrangement and that of the solution proposed hereinwas carried out by a computational fluid-dynamics program, by setting asconditions, rotation of the disk at 1500 rpm (revolutions per minute),an ambient pressure at the input and output of the space, and atemperature of 20° C. (the arrows in the drawings indicate by theirdirection, length and orientation, the velocity vectors of air particlestransported through the space by the rotation of the disk). As can beseen from a comparison of FIGS. 12 and 13, the air-flow in the solutionproposed herein was more uniform, both at the input to the space and atthe output therefrom, and passed around the pillar-like elements muchbetter or, in other words, was diverted less by the impact against thepillar-like elements. From a quantitative comparison, it was found thatthe maximum velocity reached by the air in the solution proposed hereinwas slightly reduced in comparison with the maximum velocity of theknown solution, in favour of a considerable increase in the minimum airvelocity, consequently leading to an improvement or increase in thevolume flow (in litres per second of air) of more than 5% in comparisonwith the flow-rate of the known disk.

[0057] Further advantages of the solution proposed are:

[0058] the proposed transverse extent of the elements of the inner andintermediate rows (the inside rows of the band) enables improved controlof the air-flow in the space to be achieved,

[0059] the lack of overlap or space between the adjacent rows rendersthe local stiffness of the entire disk homogeneous, avoiding thedisadvantage which is present in the case of overlap (although small) ofconnection elements of adjacent rows or, in other words, avoidingcircular portions which have twice as many connection elements as otherportions, and thus avoiding regions of the band having non-homogeneousstiffness,

[0060] the provision of connecting elements having symmetrical rhombiccross-sections permits an improvement in ventilation efficiency and, inparticular, an increase in the air-flow which passes through the spaceper unit of time,

[0061] by virtue of the proposed link radii between the flat surfaces ofthe connecting elements, the achievement of a remarkable compromisebetween the provision of sharp corners and excessively rounded elementswhich, in both cases, would adversely affect the controlledtransportation of the air; in particular, the proposed radius linkingthe pillar-like elements and the plates avoids angles which aredifficult to achieve and a cross-section which is inadequate for thedesired air-flow,

[0062] by virtue of the proposed percentage of the total facing surfacesof the plates which is covered by the connecting elements, it ispossible to achieve a remarkable resistance to cracking of the brakingsurface, permitting a controlled resistance to thermal expansion of theplates which are stressed by the braking action, and

[0063] low weight of the disk.

[0064] The main steps of the production of the disk according to thepresent invention by casting are illustrated in FIGS. 5 to 8. FIGS. 5and 6 show a core box 34 comprising a half-shell 36 to be arranged ontop and a half-shell 38 to be disposed at the bottom. In FIG. 5, the twohalf-shells are separated whereas, in FIG. 6, they are coupled and acavity 40 is defined inside them. The upper half-shell 36 has asubstantially circular structure extending about an axis X-X. In acentral position concentric with the axis X-X, there is a duct 42 forthe core sand which, by occupying the cavity 40, will give rise to acore 44, for example, shown in FIG. 7, suitable for producing a brakingband as described above. At least a portion of an inner surface 37 ofthe above-mentioned half-shell follows substantially the shape of theinner surface of the first plate 16 and of the bell 12. In particular,it can be seen that the profile concerned is of the type shown in FIG.4, that is, a profile in which the first plate 16 has a flat portion andan arcuate portion disposed in the vicinity of the bell.

[0065] The lower half-shell 38 also has a substantially circularstructure extending about the axis X-X. In a central position,concentric with the axis X-X, there is a cylindrical protuberance 46facing the duct 42 of the upper half-shell 36.

[0066] In the lower half-shell 38 as well, at least a portion of aninner surface 38 substantially follows the shape of a portion of thedisk and, in particular, of the inner surface of the second plate 18.

[0067] When the two half-shells are coupled, as shown in FIG. 6, theperipheral portion of the cavity 40 has the structure of a ring 48 whichhas a depth greater than that of the adjoining portion of the cavity andcan give rise to a core portion 50 which extends peripherally relativeto the core.

[0068] With reference to FIG. 6, a region of the cavity 40 which, in thesubsequent steps of the process will give rise to the space in thebraking band, that is, the region substantially interposed between theannular ring 48 and the protuberance 46, is indicated 51. Projectingelements 52, 54 and 56, the shape and distribution of which depends onthe shape and the distribution of the pillar-like elements 24-28 of thedisk, extend through this region.

[0069] In particular, the projecting elements 52 are such as to form inthe core 44 corresponding cavities which in turn can give rise to thepillar-like elements 24 of the inner row of the disk 10. Similarly, theprojecting elements 54 are such as to form in the core 44 correspondingcavities which in turn can give rise to the pillar-like elements 26 ofthe intermediate row and, finally, the projecting elements 56 are suchas to form in the core 44 corresponding cavities which in turn can giverise to the pillar-like elements 28 of the outer row.

[0070] Consequently, in an area parallel to the direction of flow ofsand through the cavity 40, the projecting elements 52-56 havecross-sections similar to the cross-sections of the respectivepillar-shaped elements 24-28.

[0071] As shown in FIGS. 5, 6, 10 and 11, the projecting elements 54 and56 extend through a portion of the depth of the cavity 40 between thetwo half-shells equal to approximately half of this depth. In fact, theprojecting elements 54 and 56 of one half-shell have a surface 58 forcontact with the respective projecting elements 54 and 56 of the otherhalf-shell.

[0072] It is also clear from FIGS. 5, 6, 10 and 11 that the projectingelements 52 corresponding to the inner row of pillar-like elements 24are associated with only one of the two-half-shells, that is, in theembodiment in question, with the upper half-shell 36, and extend throughthe entire depth of the cavity 40 between the two half-shells,contacting the inner surface 39 of the lower half-shell 38 directly. Inparticular, it is clear from FIG. 10 that the height of the projectingelements 52 is greater than that of the projecting elements 54 and 56which is in fact approximately half that of the projecting elements 52.

[0073] This configuration allows the two half-shells 36 and 38 to beopened along the axis X-X in order to remove the core 44 from the mould,even when the connecting portion between the braking band 14 and thebell 12 is arcuate, as shown, for example, in FIG. 4. In fact, theconfiguration of the disk 10 is reproduced in similar manner in theinner surfaces 37 and 39 of the core box 34 and the presence ofprojecting elements 52 integral with the upper half-shell 36 avoids thepresence of undercuts.

[0074] The method for the production of a disk as described above, andconsequently the ways in which a core box and a core as described aboveare used, are described below.

[0075]FIG. 5 shows the two half-shells at the stage in which they arebrought together along the axis X-X. When the two half-shells arecoupled as shown in FIG. 6, core sand is sent into the cavity 40 definedby the two half-shells, through the duct 42. The core sand is anagglomerate of sand and resins which polymerize as a result of theheating of the walls of the core box.

[0076] The particular shape of the projecting elements 52, the shape ofwhich depends on the shape of the pillar-like elements 24, favours theflow of sand into the core box and ensures that the compactnessnecessary for the subsequent success of the casting is achieved even inthe peripheral regions of the braking band.

[0077] The sand in fact maintains a high velocity up to the periphery ofthe core and this is influenced positively by the taper of theprojecting elements 52 (corresponding to the pillar-like elements 24)which limit disturbances in the flow of sand.

[0078] When the sand has been compacted, the two half-shells are removedin the directions defined by the axis X-X and the core 44 is removedfrom the mould and is as shown in FIG. 7.

[0079] The core 44 is then inserted in a mould formed in sand for thecasting of the disk 10.

[0080] It can be appreciated from the foregoing that the provision forthe pillar-shaped elements 24 disposed in the vicinity of the edge ofthe braking band that faces towards the axis Z-Z to have a cross-sectiontapered towards the axis Z-Z and, in particular, tapered in bothdirections to form a rhombic cross-section in an area substantiallyparallel to the direction of the air-flow through the space, isparticularly advantageous.

[0081] A configuration of this type is in fact reflected in a similarconfiguration of the projecting elements 52 and hence in a optimaldegree of compactness of the core used for the casting of the disk.

[0082] The fact that it is possible to use a core having optimalcharacteristics of compactness consequently affects the quality of thedisk produced and reduces subsequent processing. In particular, themasses of the disk are uniformly distributed and the step of thebalancing of the masses of the disk is less onerous, particularly withregard to the amount of mass removed. Moreover, the advantageousconfiguration of the core box, and consequently of the core, permit theproduction of a disk which, throughout the space 20, is substantiallyfree of imperfections or blockages which would adversely affect theair-flow therein. The presence of an inner row of pillar-like elements24 such as those described above enables the presence of the pillar-likeelements also to be extended to the vicinity of the bell, particularlyin embodiments which provide for a deviation of the first plate 16 andof the space 20 as shown, for example, in FIG. 4. In these, conditions,the presence of the projecting elements 52 enables the core to beremoved easily from the core box by avoiding undercuts.

[0083] Moreover, the above-described arrangement is particularlyadvantageous, for example, for disks in which the bell and the banddefine a single element. In this case, owing to the shape which the diskwill have to adopt, the passageway for the core sand through the cavitymay in fact be particularly tortuous because of the presence of acontinuous wall between the bell and the braking band.

[0084] The above-described arrangement may also be advantageous fordisks in which the braking band is connected to the bell by means ofconnecting elements having a first end fixed to the braking band and asecond end, associated slidably with the bell. In this case, in fact,the flow of sand along the core box may also be tortuous and subject toturbulence which would limit the compactness of the core, particularlyin the regions which face the outer side of the band in the region ofthe outer row of projecting elements 56 corresponding to the pillar-likeelements 28.

[0085] Naturally variants and/or additions may be provided for theembodiments described and illustrated above.

[0086] The arrangement of the pillar-like elements and of thecorresponding projecting elements may vary. In this case, theadvantageous configuration of the pillar-like elements of the inner row,as described above, applies to any of the pillar-like elements which aredisposed in the vicinity of the edge of the braking band facing the axisZ-Z. These pillar-like elements correspond to the projecting elementswhich are reached first by the flow of core sand during the formation ofthe core 44.

[0087] Naturally, the number of pillar-like elements and the shape ofthe cross-sections of the elements of the outer row and of theintermediate row or, in any case, of the pillar-like elements which arenot disposed in the vicinity of the edge of the braking band facing theaxis Z-Z, may vary.

[0088] In order to satisfy contingent and specific requirements, aperson skilled in the art may apply to the above-described preferredembodiment of the braking band, of the disk, and of the core box manymodifications, adaptations and replacements of elements with otherfunctionally equivalent elements without, however, departing from thescope of the appended claims.

1. A braking band (14) for a disk-brake disk (10) comprising two plates(16, 18) coaxial with an axis (Z-Z), facing one another, and spacedapart to form a space (20) for an air-flow from the axis (Z-Z) towardsthe outer side of the band (14), the plates (16, 18) having facingsurfaces (22) from which pillar-like elements (24, 26, 28) extend,transversely, to connect the plates (16, 18), the pillar-like elements(24, 26, 28) being distributed in circular rings or rows concentric withthe plates (16, 18) so as to be distributed uniformly in the space (20),those pillar-like elements (24, 26) which are disposed in inside rows ofthe band having rhombic cross-sections, the cross-sections beingconsidered in an area substantially parallel to the direction of theair-flow through the space (20), characterized in that radial ends ofthe cross-sections of adjacent rows are substantially aligned on acommon circle, and in that the pillar-like elements (24, 26, 28) of eachrow have substantially the same radial extent in the said cross-section.2. A braking band according to claim 1 in which the rhombiccross-sections of the pillar-like elements (24, 26) which are in insiderows of the band (14) are symmetrical with respect to an axis transversethe direction of flow.
 3. A braking band according to claim 1 or claim 2in which each element (24, 26, 28) suitable for connection between theplates (16, 18) extends from one plate to the other (16, 18) whilstremaining within the space (20).
 4. A braking band according to at leastone of the preceding claims in which the pillar-like elements (24, 26,28) interconnect the plates (16, 18) over an area no greater than15%-25%, preferably 20% of the total facing surface area of each plate.5. A braking band according to at least one of the preceding claims inwhich the pillar-like elements (24, 26) have linked flat surfacesdelimiting the rhombic cross-sections.
 6. A braking band according to atleast one of the preceding claims in which the two plates (16, 18) areconnected by pillar-like elements (24, 28) disposed along at least oneinner row and one outer row which are concentric with one another.
 7. Abraking band according to claim 6 in which the pillar-like elements (28)of the outer row have a substantially drop-shaped cross-section in anarea substantially parallel to the direction of the air-flow through thespace (20).
 8. A braking band according to claim 7 in which thesubstantially drop-shaped cross-section of the pillar-like elements (28)of the outer row is tapered towards the axis (Z-Z) of the plates (16,18).
 9. A braking band according to at least one of claims 6 to 8 inwhich one or two further intermediate rows of pillar-like elements (26)are provided.
 10. A braking band according to at least one of thepreceding claims in which the pillar-like elements (24) of the inner rowhave, in an area substantially parallel to the direction of the air-flowthrough the space (20), a diagonal of the rhombic cross-sectiontransverse the direction of flow having dimensions of between 6 mm and 7mm.
 11. A braking band according to at least one of the preceding claimsin which the pillar-like elements (26) of the at least one intermediaterow have, in an area substantially parallel to the direction of theair-flow through the space (20), a diagonal of the rhombic cross-sectiontransverse the direction of flow having dimensions of between 7 mm and 8mm.
 12. A braking band according to at least one of the preceding claimsin which the pillar-like elements (26) of the at least one intermediaterow are offset relative to those (24, 28) of the inner row and of theouter row.
 13. A braking band according to at least one of the precedingclaims in which the pillar-like elements (24, 26, 28) are distributed ina quincuncial arrangement between the two plates (16, 18).
 14. A brakingband according to at least one of the preceding claims in which thepillar-like elements (24, 26) of the inner and intermediate rows have,in a radial direction, ends with link radii variable from 1.5 mm to0.2.5 mm, preferably 2 mm.
 15. A braking band according to at least oneof the preceding claims in which the pillar-like elements (28) of theouter row have, in a radial direction, a first end with a link radiusvariable from 1.5 to 2.5 mm, preferably 2 mm, and a second end with alink radius variable from 4 mm to 5 mm, preferably 4.5 mm.
 16. A brakingband according to at least one of the preceding claims in which thepillar-like elements (24) of the inner row have, in a directiontransverse the direction of flow, link radii variable from 3 mm to 3.5mm between the flat surfaces.
 17. A braking band according to at leastone of the preceding claims, in which the pillar-like elements (26) ofthe at least one intermediate row have, in a direction transverse thedirection of flow, link radii variable from 3.5 mm to 4 mm between theflat surfaces.
 18. A braking band according to at least one of thepreceding claims in which the pillar-like elements (24, 26, 28) areconnected to the plates (16, 18) with link radii variable from 3 mm to 4mm, preferably 3.5 mm.
 19. A disk-brake disk (10) comprising a brakingband (14) according to any one of the preceding claims.
 20. A disk-brakedisk according to claim 19 in which the braking band (14) does not haveelements for connection to a bell (12) which have a first end fixed tothe braking band (14) and a second end associated slidably with the bell(12).
 21. A disk-brake disk according to claim 19 in which a plate (16)of the braking band (14) is connected to a bell (12).
 22. A core box(34) for the production of a core (44) for a disk-brake disk (10),comprising two half-shells (36, 38) which, when coupled, define a cavity(40), and of which at least one has elements (52) projecting towards theother through the cavity (40) to produce in the core (44) cavities forforming pillar-like elements (24) which extend to connect plates (16,18) constituting a braking band (14) of the disk, as defined in any oneof claims 1 to
 18. 23. A core box according to claim 22 in which theprojecting elements (52) are distributed around a circular ring or rowconcentric with the respective half-shell (36).
 24. A core box accordingto claim 23 in which each of the two half-shells (36, 38) comprisesfurther projecting elements (54, 46) which extend through a portion ofthe depth of the cavity (40) between the two half-shells.
 25. A core boxaccording to claim 24 in which the further projecting elements (54, 56)of one half-shell have a surface (58) for contact with respectivefurther projecting elements (54, 56) of the other half-shell.
 26. A corebox according to claim 24 or claim 25 in which the further projectingelements (54, 56) are distributed around at least one circular ring orrow concentric with the respective half-shell.